Respectfully, you're asserting a definition - which may be true, but why is your definition any more true than anyone else's? Because the symptom has no objective test, it's open to interpretation. In other words, consensus. And my point is, that there's really no consensus here.
CDC: "PEM is worsening of ME/CFS symptoms after physical or mental activity that wouldn’t have caused problems previously."
CDC: "Post‑exertional malaise (PEM) is the worsening of symptoms following even minor physical or mental exertion that would have been tolerated previously. Symptoms typically worsen 12 to 48 hours after activity and can last for days or even weeks."
SolveME: " 'worsening of symptoms following even minor physical or mental exertion' with delayed onset and duration of 'days or even weeks.' "
Bateman Horne: "PEM is the worsening of a patients’ symptoms and function after exposure to physical, cognitive, emotional, or orthostatic stressors that were normally tolerated before disease onset"
NICE: "The worsening of symptoms that can follow minimal cognitive, physical, emotional, or social activity, or activity that could previously be tolerated. Symptoms can typically worsen 12 to 48 hours after activity and last for days or even weeks, sometimes leading to a relapse. Post‑exertional malaise may also be referred to as post‑exertional symptom exacerbation."
Whereas other people can and do claim that post-exertional symptom exacerbation is something completely different.
OMF: "marked by a significant worsening of symptoms or the development of flu‑like symptoms following physical or mental exertion"
At least psychitry has the DSM to drive consensus. We don't have that here. These are similar, but differ in key ways.